How do you see the beam of a flashlight in the dark? Because it hits stuff in the air and bounces off. And the particles previously in the beam that already h

How do you see the beam of a flashlight in the dark? Because it hits stuff in the air and bounces off. And the particles previously in the beam that already hit something are likely to hang around and be candidates for being hit themselves. And eventually they wind up as part of a big glowing cloud that you can see in the pictures. See https://d2r55xnwy6nx47.cloudfront.net/uploads/2021/05/cyga_v1.jpg https://d2r55xnwy6nx47.cloudfront.net/uploads/2021/05/cyga_v... linked in the picture for what it looks like. And for evidence that we can still see the beam when it isn't pointed directly at us.